1. Field of the Invention
This invention relates to a common conductor assembly, more particularly to a common conductor assembly for a contact switch.
2. Description of The Related Art
Referring to FIGS. 1 and 2, a conventional common conductor assembly is employed in a contact switch and includes a mounting plate 12, a pivotally movable member 13 and a tension spring 14. The contact switch includes a lower switch casing part 10, an upper switch casing part 11 connected to the lower switch casing part 10 to form a switch casing, a push button 15 and first and second conductors 16, 17. The mounting plate 12 is provided on the lower switch casing part 10 and has an elongated flat portion 120 with first and second vertical edges, and first and second end plate portions 125, 122 extending integrally and transversely from a respective one of the first and second vertical edges in a same direction. The first end plate portion 125 has an outward face formed with an engaging groove 126 that is perpendicular to the vertical edges of the elongated flat portion 120, and an upper edge formed with a notch 127. The second end plate portion 122 has a spring mounting hole 121 formed therethrough, and a distal end formed with a notch 124. A conducting leg plate portion 121 extends downwardly and integrally from the second vertical edge of the elongated flat portion 122 and through the lower switch casing part 10. The pivotally movable member 13 has an engaging end received in the engaging groove 126 of the first end plate portion 125, and a spring engaging hole 131 formed therethrough. The tension spring 14 has a first hook end and a second hook end. The first hook end of the tension spring 14 extends through the notch 127 of the first end plate portion 125 to engage the spring engaging hole 131, while the second hook end of the tension spring 14 extends through the notch 124 of the second end plate portion 122 to engage the spring mounting hole 123 so as to interconnect the movable member 13 and the mounting plate 12 under tension in order to permit movement of the movable member 13 between upper and lower positions when the push button 15 is pressed. Each of the first and second conductors 16, 17 has a downwardly extending leg portion which projects out of the lower switch casing part 10 in the same direction as the conducting leg portion 121 of the mounting plate 12. The first and second conductors 16, 17 have contact portions which are disposed inside the switch casing and which extend respectively above and below the movable member 13. The push button 15 is in contact with a portion of the tension spring 14, which portion is adjacent to the first hook end of the tension spring 14. The push button 15 is operable to actuate the tension spring 14 to move the movable member 13 between the upper position, wherein the movable member 13 is in contact with the first conductor 16, and the lower position, wherein the movable member 13 is in contact with the second conductor 17. The notch 124 of the second end plate portion 122 prevents the second hook end of the tension spring 14 from any vertical movement. The notch 127 of the first end plate portion 125 prevents the misplacement of the tension spring 14 in the first end plate portion 125 when the tension spring 14 is actuated.
The main drawback of the aforementioned conventional contact switch resides in the mounting of the tension spring 14. Since the spring mounting hole 121 of the second end plate portion 122 does not lie in the same orientation as that of the spring engaging hole 131 of the movable member 13, full automation of the mounting procedure of the tension spring 14 to interconnect the second end plate portion 122 and the movable member 13 is difficult, thereby resulting in waste of labor, a longer production time and a lower production rate. In addition, a manual mounting operation often results in poorer quality.